1. Field of the Invention
The invention relates to a lighting device, and more particularly to a lighting device suitable for use as a light source.
2. Description of the Related Art
A liquid crystal display (LCD) includes a panel and a backlight module that provides a light source for image display. For uniform illumination of a large area, the conventional backlight module includes a plurality of lighting devices disposed in an area having the same size as the panel and in an array arrangement.
Referring to FIG. 1, a lighting device disclosed in Taiwan patent no. 1352795 includes a light emitting component 5 and a light control component 6. The light emitting component 5 provides an incident light 51.
The light control component 6 is made of a light-transmissive material having a refractive index, and has a datum point 63, a main axis 64 passing through the datum point 63, a light incident surface 61, and a light exit surface 62. The light emitting component 5 is disposed on the datum point 63. The light incident surface 61 is disposed to receive light from the light emitting component 5, allows passage of the incident light 51, and is axis symmetrical relative to the main axis 64. A line connecting the datum point 63 and an arbitrary point disposed on the light incident surface 61 is defined as a first line R1, and an included angle of the main axis 64 and the first line R1 is defined as a first angle α1. The light incident surface 61 is configured such that, when the first angle α1 is smaller than 60 degrees, a length of the first line R1 decreases in a monotonic manner with increase of the first angle α1.
The light exit surface 62 is spaced apart from the light incident surface 61, and is a curved surface that is axis symmetrical relative to the main axis 64. A line connecting an arbitrary point disposed on the light exit surface 62 and the datum point 63 is defined as a second line R2. An included angle of the main axis 64 and the second line R2 is defined as a second angle α2. The light exit surface 62 is configured such that, when the second angle α2 is smaller than 60 degrees, a length of the second line R2 increases in a monotonic manner with increase of the second angle α2. The light control component 6 has light diffusion characteristics through configurations of the light incident surface 61 and the light exit surface 62, and allows passage of light to the panel.
However, better light diffusion requires larger curvature of the light incident surface 61, which results in a concavity with a large depth-width ratio formed in the light incident surface 61, such that the thickness of the light control component 6 is increased, which goes against the trend toward reducing thickness of the backlight module. Moreover, large thickness difference between the portion of the light control component 6 that is disposed close to the main axis 64 and the portion of the light control component 6 that is disposed relatively far from the main axis 64 may result in a junction line during production and a longer forming time.